Historically, numerous grades of polyurethane foams were blown with chlorofluorocarbon (CFC) based blowing agents to reduce foam density, control foam firmness and to cool the foams to minimize discoloration, degradation and possible foam ignition problems. World-wide issues regarding ozone depletion in connection with certain CFCs has led to the Montreal Protocol, which phases out the production of CFCs.
Thus, the polyurethane foam industry has tried to achieve the same foam grades and quality produced using alternate blowing agents (ABAs). Many different ABAs have been evaluated including HCFC-141b, HFC-134a, HFC-22, alkyl carbonates and pentane. In flexible slabstock foams in particular, other approaches have been taken, including the use of acetone, methylene chloride, carbon tetrachloride, trichloroethane, and pentane as ABAs. While functional, these approaches also have problems including flammability (for acetone and pentane) and toxicity (for the chlorocarbons).
More recently, a technology has been developed which entails the use of supplemental added inert gases, e.g., CO.sub.2, as part of the blowing agent for flexible polyurethane foams, which is described in European Patent Publication No. 0 645 226 A2 (hereinafter "Dissolved Gas Technology"). Auxiliary gas is added to the system as a blowing agent and is used in conjunction with the CO.sub.2 generated from the reaction of isocyanate with water. However, this prior art focuses on the details of a process for frothing a slabstock foam reaction mixture using liquid CO.sub.2 with special equipment and does not teach what type of silicone surfactant should be used therein.
The prior art does teach a myriad of silicone surfactants for use in polyurethane foams, but none are directed to Dissolved Gas Technology, see U.S. Pat. Nos. 5,145,879 and 4,814,409. The standard structures do not provide teachings as to which surfactants would work and many of these surfactants do not work in stabilizing the foam or providing uniform cell size.